The invention relates to a drive unit for a vertical blind or the like wherein vertically oriented slats are movable by a pull element, such as a pull chain or cord, and an electric drive motor is provided for operation of the pull element. The invention also relates to a vertical blind equipped with such a drive unit.
Vertical blinds consisting of a multiplicity of lamellar, rigid slats hanging vertically next to each other and which can be pulled along an upper support guide rail as well as pivoted around a vertical axis, are being used increasingly, especially in the commercial sphere, i.e., for office spaces, etc. The slats of such vertical blinds are typically moved by a pull element that runs in the upper support guide rail, namely, with modern, convenient, easy to use vertical blinds, the slats are pulled and pivoted by a pull element in the form of a single pull chain or cord. Often, this kind of pull element is a traction rope with catch beads knotted in or otherwise attached. Instead of a pull chain, other pull elements, for example, a wire rope encased in plastic or the like, are also known. Similar operating relationships as those used in vertical blinds also are found in some normal curtains and other decorations that are to be pulled.
In vertical blinds operated by hand, the pull element, in particular the pull chain or cord, hangs down from the support guide rail on one end of the vertical blinds, far enough so that an operator can pull the pull chain or cord by hand. Normally, in doing so the pull chain or cord moves in an endless circuit. In more convenient vertical blinds, an electromotive drive unit is provided that is put directly on the support guide rail, at one end of the vertical blind. An associated switch control, usually a simple ON/OFF stop switch, is placed at a separate location from the housing of the drive unit, for example, at an appropriate place on the nearest wall or the like. The switch control is normally connected to the electric drive motor in the housing of the drive unit by a cable that is, generally, laid under plaster.
The problem with the known drive unit, described above, centers on the fact that it is not especially easy to retrofit it on existing hand-operated vertical blinds. To retrofit it, the pull element, in particular the pull chain or cord, must first be shortened and then rejoined so that it is tensioned with an accurate fit around the drive pinion in the housing of the drive unit placed on the guide rail. A box for the switch control must be put on the nearest wall and connected by junction cable to the housing of the drive unit. Even if, with greater engineering expense, a wireless connection between the switch control and the electric drive motor of the drive unit is considered, retrofitting is still not especially simple and is expensive in any case.
In addition, with the previously explained known drive unit for vertical blinds, hand operation, if possible, is achieved only with difficulty. Here, it must be taken into consideration that the slats of such vertical blinds are damaged relatively easily when pulled by hand. As a result, it has already been devised that, on the reduction gear in the drive unit housing, which is fastened to the guide rail, a plug-in socket for a mechanical operating crank is provided that is accessible from the exterior of the housing. It can easily be imagined how laborious this type of hand operation is. The result is that, when the electrical drive motor or the switch control fails, for convenience, an operator often attempts to move the blinds merely by pulling on them and they are, thus, damaged.
Of course, disengageable motor driven, endless chain drive operators are old and commonly well known. Likewise, from, for example, U.S. Pat. No. 2,029,143, it has long been known that for large Venetian blinds, such as those suitable for large department store windows, the endless chain pull element of the blind may be provided with a motor with a drive sprocket about which the hanging lower end of the chain is looped so as to enable operation of the blind at a distance via a suitably placed motor switch, while still retaining the ability to manually operate the Venetian blind.
However, vertical blinds are selected as much as an element of an attractive decorating scheme (the slats usually being made of a wide range of fabric and other decorative materials, as opposed to a typical utilitarian metal-slatted Venetian blind) as for its functional purpose in controlling natural lighting. Thus, for this reason, in addition to equally important safety considerations, it is highly undesirable to merely utilize a drive unit wherein the drive sprocket, drive motor and the like are exposed in a manner creating an unattractive appearance and potential source of injury.